Have my cake and eat it too..

Currently in my Valiant is a built up 904. it has a manual valve body in it and the 1-2 shift is teeth rattling while sanely driving it, but feels perfectly smooth and appropriate at WFO. The 2-3 shift is pretty stout as well, but I can atleast smooth that out by slightly lifting.
What I'm wondering, is there a modern transmission that can be moved back and forth with a button from getting groceries setting, to losing my license setting? Ofcourse the extra gears are welcomed, but I wouldn't go through all the hassle and money of a modern upgrade for just that, it has to be a major improvement.